(1) Field of the Invention
The present invention relates to a control device for controlling an aircraft, to such an aircraft fitted with a control device of this type, and to a corresponding control method enabling a pilot to control an aircraft, e.g. such as an airplane or a rotorcraft.
The invention seeks more particularly to provide a control device in which a trim actuator is placed in parallel in a main control linkage serving to control aerodynamic means of an aircraft. The trim actuator constitutes in particular a system for providing the pilot with assistance by making it easier to hold a control member in a determined position.
Specifically, such an aircraft also includes at least one control member that is to be moved by at least one pilot in order to move aerodynamic means.
(2) Description of Related Art
Thus, below in the present application, the term “control member” is used to designate any control device that can be moved by a pilot or automatically, whether in a cockpit or outside the aircraft if the aircraft does not have a pilot on board. Such control members may thus present various forms and in particular they may be in the form of a lever, a stick, a mini-stick or “joystick”, or indeed pedals.
Such control members then serve to move aerodynamic means relative to an air stream that is incident on a fuselage of the aircraft. In an airplane, such aerodynamic means may then consist by way of example either in flaps, ailerons, or wing spoilers, or else by way of example in a rudder of a tail fin or an elevator.
In a rotorcraft, such aerodynamic means may nevertheless correspond by way of example to a collective pitch angle or cyclic pitch angle for the blades of a main rotor and to a collective pitch angle in particular for the blades of a tail rotor, for example.
Furthermore, an aircraft generally includes a plurality of trim actuators for controlling a plurality of aerodynamic means. Such trim actuators may then be of the “anchored motor-driven” type so as to generate an opposing force in a control member of the aircraft on the basis of an opposing torque generated by at least one electric motor of the trim actuator. Furthermore, such trim actuators may also be of the active type: under such circumstances, the force gradient of the opposing torque generated by the electric motor(s) may vary with a varying “anchor” position of the trim actuator.
Furthermore, in order to control such a trim actuator, it is necessary to servo-control a control setpoint for the electric motor(s) in such a manner as to guarantee optimum operation of the various members.
For this purpose, and as described in particular by the following documents: FR 2 718 102; FR 2 989 353; US 2016/0221674; U.S. Pat. No. 8,942,866; US 2005/0080495; and U.S. Pat. No. 7,108,232; control devices have been developed that include in particular a so-called “force” servo-control loop for controlling the electric motor(s) of the trim actuator. Under such circumstances, such servo-control loops are implemented by means of force sensors measuring a force exerted on a control linkage of the control member. In this way, it becomes possible to adapt the control setpoint for the electric motor as a function of the measured force acting on the control linkage of the control member. The force servo-control loop is then generally combined with an electric current servo-control loop in order to generate the control setpoint for the electric motor(s) of the trim actuator.
Nevertheless, such control devices do not make dynamic anchoring possible for a series actuator arranged in series with the main control linkage for controlling the aerodynamic means of the aircraft. Specifically, any variation in the position of a control member automatically gives rise to a variation in its travel speed and thus in the speed of an outlet shaft or of an outlet lever of the trim actuator. This speed variation is thus not taken into account by such control devices, which can be problematic, giving rise to jolting in the control member.
Furthermore, the motor(s) of a trim actuator of that type of control device is/are then the subject of servo-control that is not very robust, and in any event is not optimum.